The Messenger of Allah ﷺ said the Qunut for one month, supplicating against one of the 'Arab tribes, then he stopped doing that." (Using translation from Nasāʾī 1079)
قَنَتَ رَسُولُ اللهِ ﷺ شَهْرًا بَعْدَ الرُّكُوعِ يَدْعُو عَلَى حَيٍّ مِنْ أَحْيَاءِ الْعَرَبِ ثُمَّ تَرَكَهُ